Abstract:

It is possible to provide a core network device, a radio communication
base station device, and a radio communication method which can improve
the radio resource use efficiency of the entire network without
increasing UE battery consumption. According to the devices and the
method, a user quantity counting unit (163) of UPE (160) counts the
number of UE which have performed a position registration in each
position registration area containing a plurality of cells. A user
quantity comparing unit (164) selects MCT if the counted UE quantity is
not smaller than a predetermined threshold value and SCT if the counted
UE quantity is smaller than the predetermined threshold value, thereby
appropriately performing switching between SCT and MCT in accordance with
the UE quantity. Only when the SCT is selected by the UPE (160), eNB
counts the number of users in the cell managed by the local device.

Claims:

1. A core network apparatus comprising:a user number counting section that
counts a number of users joining a multimedia broadcast multicast service
(MBMS) on a per tracking area basis;a user number comparing section that
compares the number of users counted, with a predetermined threshold, so
as to select, when the number of users is equal to or greater than the
threshold, multi-cell transmission whereby a plurality of radio
communication base station apparatuses belonging to an identical
frequency area transfer multimedia broadcast multicast service data in
synchronization with each other, and select, when the number of users is
less than the threshold, single cell transmission whereby a single radio
communication base station apparatus accommodating users joining the
multimedia broadcast multicast service in a cell, transfers multimedia
broadcast multicast service data; anda reporting section that reports one
of multi-cell transmission and single cell transmission selected, to a
radio communication base station apparatus under control.

2. The core network apparatus according to claim 1, further comprising a
distribution check section that selects, when the user number comparing
section selects single cell transmission, a transmission mode based on a
situation of distribution of radio communication base station apparatuses
subject to single cell transmission.

3. The core network apparatus according to claim 2, wherein the
distribution check section selects multi-cell transmission when a ratio
of the number of radio communication base station apparatuses subject to
single cell transmission to a total number of radio communication base
stations per tracking area is equal to or greater than a predetermined
threshold.

4. A radio communication base station apparatus comprising:an acquisition
section that acquires from a core network apparatus a command for one of
multi-cell transmission whereby a plurality of radio communication base
station apparatuses belonging to an identical frequency area transfer
multimedia broadcast multicast service (MBMS) data in synchronization
with each other and single cell transmission whereby a single radio
communication base station apparatus accommodating users joining the
multimedia broadcast multicast service within a cell transfers the
multimedia broadcast multicast service data;a counting section that
performs counting about a cell under control of the radio communication
base station apparatus only when a single cell transmission command is
acquired; anda transfer section that transfers the multimedia broadcast
multicast service data in a cell where there are users according to the
counting result.

5. The radio communication base station apparatus according to claim 4,
wherein, upon acquiring a command for single cell transmission, the
counting section causes the radio communication terminal apparatus inside
a cell under control of the radio communication base station apparatus to
transition into an active mode for only a control channel and counts the
number of users, on a per cell basis.

6. The radio communication base station apparatus according to claim 4,
further comprising:a detection section that acquires a received quality
measurement result in a nearby cell measured by a radio communication
terminal apparatus and detects a radio communication terminal apparatus
located in cell edges based on the acquired received quality measurement
result; anda multicast processing section that requests, when detecting
the radio communication terminal apparatus located in the cell edge, a
neighboring cell forming the cell edge, to join multimedia broadcast
multicast service.

7. The radio communication base station apparatus according to claim 4,
further comprising:a recounting period selection section that selects a
recounting period, which is an interval until next counting is performed;
anda parameter selection section that selects a response probability,
which is a condition for the radio communication terminal apparatus that
requests multimedia broadcast multicast service to send a response
message, wherein:upon acquiring a command for single cell transmission,
the counting section controls the recounting period selection section and
the parameter selection section, so as to extend a recounting period and
reduce a response probability when the number of users inside the cell is
equal to or greater than a predetermined threshold or shorten the
recounting period and increase the response probability when the number
of users inside the cell is less than the predetermined threshold.

8. The radio communication base station apparatus according to claim 4,
further comprising a multicast processing section that inquires of other
radio communication base station apparatuses located in the boundary
between neighboring tracking areas about the multimedia broadcast
multicast service delivery situation and requests the other radio
communication base station apparatuses that do not provide multimedia
broadcast multicast service to join multimedia broadcast multicast
service.

9. The radio communication base station apparatus according to claim 4,
further comprising:a detection section that detects, upon acquiring a
negative acknowledgement for requesting a retransmission of lost
multimedia broadcast multicast service data and a received quality
measurement result in a neighboring cell measured by the radio
communication terminal apparatus, a radio communication terminal
apparatus located in cell edges based on the acquired received quality
measurement result;a counting section that counts the number of users
located in the cell edge detected by the detection section for each
neighboring cell;a multicast processing section that requests, when the
number of users counted for each neighboring cell is equal to or greater
than a predetermined threshold, the neighboring cell to join multimedia
broadcast multicast service; anda retransmission section that
retransmits, when the number of users counted for each neighboring cell
is less than the predetermined threshold, the multimedia broadcast
multicast service data requested by the negative acknowledgment.

10. The radio communication base station apparatus according to claim 9,
wherein the counting section counts the number of users located in cell
edges bordering on a specific neighboring cell.

11. A radio communication terminal apparatus comprising:a data decision
section that decides whether or not received multimedia broadcast
multicast service data is lost and creates, upon deciding that the
multimedia broadcast multicast service data is lost, a negative
acknowledgment message for requesting a retransmission of the lost
multimedia broadcast multicast service data;a received power measurement
section that measures received power in each neighboring cell; anda
transmission section that transmits the negative acknowledgment message
and received power measurement result in each neighboring cell to a radio
communication base station apparatus.

12. The radio communication terminal apparatus according to claim 11,
wherein the received power measurement section measures received power in
a specific neighboring cell.

13. A radio communication method comprising:counting, by a core network
apparatus, a number of users joining a multimedia broadcast multicast
service (MBMS) on a per tracking area basis;comparing, by a core network
apparatus, the number of users counted, with a predetermined threshold,
so as to select, when the number of users is equal to or greater than the
threshold, multi-cell transmission whereby a plurality of radio
communication base station apparatuses belonging to an identical
frequency area transfer multimedia broadcast multicast service data in
synchronization with each other, and select, when the number of users is
less than the threshold, single cell transmission whereby a single radio
communication base station apparatus accommodating a user joining the
multimedia broadcast multicast service within a cell transfers multimedia
broadcast multicast service data;reporting, by a core network apparatus,
one of multi-cell transmission and single cell transmission selected, to
radio communication base station apparatuses under control of the core
network apparatus;acquiring, by a radio communication base station
apparatus, a command for one of multi-cell transmission and single cell
transmission, from the core network apparatus,counting, by a radio
communication base station apparatus, about the cell under control of the
radio communication base station apparatus only when a single cell
transmission command is acquired; andtransferring, by a radio
communication base station apparatus, multimedia broadcast multicast
service data in a cell where there are users according to the counting
result.

Description:

TECHNICAL FIELD

[0001]The present invention relates to a core network apparatus, radio
communication base station apparatus and radio communication method for
providing a multimedia broadcast/multicast service (MBMS).

BACKGROUND ART

[0002]UMTS (Universal Mobile Telecommunications System) is a
third-generation mobile communication system which has evolved from GSM
(Global System for Mobile Communications), which is the European standard
and aims at providing further improved mobile communication services
based on a GSM core network (CN) and a WCDMA (Wideband Code Division
Multiple Access) wireless access technique.

[0003]UMTS provides MBMS. MEMS is a more developed service for not only
broadcasting multimedia data but also multicasting multimedia to users
who subscribe to applicable services. For example, MBMS provides a news
channel, music channel, movie channel or the like.

[0006]UTRAN 20 is comprised of one or more radio network sub-systems
(RNS), and an RNS is comprised of one radio network controller (RNC) 23
and one or more Nodes B (base stations) 21 under control of appropriate
RNC 23.

[0007]RNC 23 is responsible for allocation and management of radio
resources and plays a role as an access point with respect to CN 30.

[0008]Node B 21 receives information transferred from the physical layer
of UE 10 via the uplink, or on the contrary, transfers data to UE 10 via
the downlink. Node B 21 assumes a role of access point of UTRAN for UE
10.

[0009]UTRAN 20 makes up and maintains a radio access bearer (RAB) for a
call between UE 10 and CN 30.

[0010]CN 30 requests end-to-end service quality (Quality of Service: QoS)
requirements from the RAB and the RAB supports the QoS requirements set
up by CN 30. Therefore, UTRAN 20 makes up and maintains the RAB, and
therefore meets the end-to-end QoS requirements.

[0011]MBMS is provided via a packet switching service. When providing a
packet switching service, RNC 23 is connected to SGSN (Serving GPRS
Support Node) 35 and GGSN (Gateway GPRS Support Node) 37 of CN 30. SGSN
35 supports communication with RNC 23 and GGSN 37 manages connections
with other packet switching networks such as the Internet.

[0012]MBMS is a downward dedicated service that provides a streaming or
background service for a plurality of UEs 10 using a common or dedicated
downward channel.

[0013]MBMS is divided into a broadcast mode and a multicast mode. In the
MBMS broadcast mode, multimedia data can be easily transferred to all
users located in a broadcast area. On the other hand, in the MBMS
multicast mode, multimedia data can be easily transferred to a specific
user group located in a multicast area. Here, the broadcast area is an
area where a broadcast service is available and the multicast area is an
area where a multicast service is available.

[0014]Users who try to receive an MBMS receive a service announcement
provided by the network. Here, the "service announcement" refers to
reporting a list of services to be provided in the future and related
information to UEs. Furthermore, users receive service notification
provided by the network. Here, "service notification" refers to notifying
the UEs of information about the broadcast data to be transferred.

[0015]Furthermore, users who want to receive an MBMS in the multicast mode
must particularly join a multicast subscription group. The "multicast
subscription group" refers to a group of users who have completed a
subscription procedure.

[0016]A user who has joined the multicast subscription group can
participate in (join) a multicast group to receive a specific multicast
service, that is, a user group who receive a specific multicast service.
The "multicast group" refers to a group of users who receive a specific
multicast service. "Joining" refers to joining a multicast group who
gather to receive a specific multicast service and is also called "MBMS
multicast activation." Therefore, the user can receive specific multicast
data through MBMS multicast activation (or joining).

[0017]RNC 23 transfers MBMS user data to UE 10 via Node B 21 through the
user plane of the UTRAN protocol. In order to transfer the MBMS user
data, UTRAN 20 makes up and maintains a radio bearer for a call between
UE 10 and CN 30. The MBMS radio bearer is transferred only through a
downlink.

[0018]The MBMS radio bearer plays a role of transferring user data of one
specific MBMS transferred from CN 30 to UTRAN 20 only to specific UEs.

[0019]Furthermore, in the case of multicast mode, UTRAN 20 needs to
confirm the presence of UEs in the entire service area to deliver MBMS
user data only to Node B 21 where users are located. Therefore, UTRAN 20
counts the number of UEs. UTRAN 20 reports UE 10 that UTRAN 20 is
currently counting when providing information about MBMS using a MBMS
common control channel or performing paging to a specific MBMS group.

[0020]Upon receiving the information that counting is being performed on
the corresponding service from the service notification on MBMS, UE 10
transfers an RRC connection request message to UTRAN through an uplink
common channel to report UTRAN 20 that UE 10 wants to receive the
corresponding MBMS and thereby sets up an RRC connection (connection
between the RRC entity of UE 10 and RRC entity of UTRAN 20). Here, UE 10
reports to UTRAN 20 that UE 10 wants to receive the corresponding MBMS
using an RRC connection request message.

[0021]Therefore, UTRAN 20 recognizes UE 10 that has transferred the RRC
connection request message and thereby recognizes the presence of the
user who requests a specific MBMS within the cell and sets up an MBMS
radio bearer if at least one user exists.

[0022]By the way, the 3GPP is currently studying a next-generation core
network and radio access network, and as for an MBMS transfer method, the
3GPP is also studying the following two transfer methods as standard
candidates along with this.

[0023]FIG. 2 shows a conceptual diagram of the two transfer methods. The
first one is called "single cell transmission (SCT)" as shown on the
right side of FIG. 2, which performs counting to check the
presence/absence of users and performs data transmission only to cells
where there are users. Furthermore, when quality deteriorates in cell
edges or the like, SCT performs retransmission or changes the modulation
scheme to thereby improve received quality of users.

[0024]The second one is called "multi-cell transmission (MCT)" as shown on
the left side of FIG. 2, whereby a plurality of base stations belonging
to the same frequency area (Single Frequency Network: SFN) perform data
transmission in synchronization with each other and improve received
quality of users through inter-cell diversity combination irrespective of
the presence/absence of users.

[0025]However, the above de scribed method for providing MBMS selects MCT
or SCT depending on a service and has the following problems.

[0026]In MCT, multimedia data is only transferred to the SFN area, and
therefore when the number of users located in the SFN area is small, the
amount of data delivered to the cell with no user increases, which may
decrease the utilization efficiency of radio resources of the entire
network.

[0027]Furthermore, in SCT, counting is performed to transfer data only to
a specific user group, but with this counting, the user needs to
establish an RRC connection with Node B and thereby consumes the battery.
For this reason, when there are many users in a given area, users exist
in most cells in the area and the amount of battery consumption of UEs
may increase by the amount corresponding to unnecessary counting compared
to MCT.

[0028]It is therefore an object of the present invention to provide a core
network apparatus, radio communication base station apparatus and radio
communication method for improving the utilization efficiency of radio
resources of an entire network without increasing battery consumption of
UEs.

Means for Solving the Problem

[0029]The core network apparatus of the present invention adopts a
configuration including a user number counting section that counts the
number of users joining a multimedia broadcast/multicast service (MEMS)
on a per tracking area basis, a user number comparing section that
compares the number of users counted, with a predetermined threshold, so
as to select, when the number of users is equal to or greater than the
threshold, multi-cell transmission whereby a plurality of radio
communication base station apparatuses belonging to an identical
frequency area transfer MBMS data in synchronization with each other, and
select, when the number of users is less than the threshold, single cell
transmission whereby a single radio communication base station apparatus
accommodating users joining the MBMS within a cell transfers MBMS data,
and a reporting section that reports one of multi-cell transmission and
single cell transmission selected, to a radio communication base station
apparatus under control.

[0030]The radio communication base station apparatus of the present
invention adopts a configuration including an acquisition section that
acquires from a core network apparatus a command for one of multi-cell
transmission whereby a plurality of radio communication base station
apparatuses belonging to an identical frequency area transfer multimedia
broadcast/multicast service (MBMS) data in synchronization with each
other, and single cell transmission whereby a single radio communication
base station apparatus including users joining the MBMS within a cell
transfers the MBMS data, a counting section that performs counting about
a cell under control of the radio communication base station apparatus
only when a single cell transmission command is acquired, and a transfer
section that transfers the MBMS data in a cell where there are users
according to the counting result.

[0031]The radio communication method of the present invention includes a
user number counting step of a core network apparatus counting the number
of users joining a multimedia broadcast/multicast service (MBMS) on a per
tracking area basis, a user number comparing step of comparing the number
of users counted, with a predetermined threshold, so as to select, when
the number of users is equal to or greater than the threshold, multi-cell
transmission whereby a plurality of radio communication base station
apparatuses belonging to an identical frequency area transfer MBMS data
in synchronization with each other, and select, when the number of users
is less than the threshold, single cell transmission whereby a single
radio communication base station apparatus accommodating a user joining
the MBMS within a cell transfers MBMS data, a reporting step of reporting
one of multi-cell transmission and single cell transmission selected, to
radio communication base station apparatuses under control of the core
network apparatus, an acquiring step of a radio communication base
station apparatus acquiring a command for one of multi-cell transmission
and single cell transmission from the core network apparatus, a counting
step of counting about the cell under control of the radio communication
base station apparatus only when a single cell transmission command is
acquired, and a transfer step of transferring MBMS data in a cell where
there are users according to the counting result.

ADVANTAGEOUS EFFECT OF THE INVENTION

[0032]According to the present invention, it is possible to improve the
utilization efficiency of radio resources of an entire network without
increasing battery consumption of UEs.

[0051]eNB 120 is in charge of allocation and management of radio
resources, receives information transferred from the physical layer of UE
100 via the uplink, and, meanwhile, transfers data to UE 100 via the
downlink. eNB 120 assumes a role as an access point of the radio access
network for UE 100.

[0052]MME 140 manages the location of UE 100 on a per tracking area basis
(TA) and also performs signaling about the setting, correction and
release of RAB jointly with UE 100. MME 140 stores a context assigned in
a network connection procedure of UE 100 and associated with MBMS of UE
100. A plurality of MMEs 140 exist in a given MBMS area and MME to which
users are connected differs from one user to another.

[0053]UPE 160 plays a role as gateway with respect to an outside network,
transfers a downlink packet to an eNB to which UE 100 is connected
according to the setting of RAB and transfers an uplink packet to an
appropriate outside network according to the destination address of a
packet. Only one UPE 160 exists within a given MBMS area for each MBMS
and stores contexts associated with MEMS.

[0054]BM-SC 180 is located between an MEMS content server and UPE 160 and
transfers information about the session type, the start and end of a
service and MBMS data to UPE 160.

[0056]User information management section 142 compares the MEMS reception
performance of UE 100 with the performance of UE 100 included in the MEMS
registration response reported from BM-SC 180 and required for the
corresponding service. When this comparison result shows that the MBMS
reception performance of UE 100 exceeds the performance of UE 100
required for the service, the service and an identifier for the tracking
area to which UE 100 belongs are reported to user number counting section
143. When the MBMS reception performance of UE 100 falls below the
performance of UE 100 required for the service, suspension of the
processing is reported to BM-SC 180 and UE 100.

[0057]User number counting section 143 counts the number of joining users,
per service, on a per tracking area basis and updates the number of users
according to the service and the tracking area identifier reported from
user information management section 142. The updated number of users is
outputted to output section 144. In this way, MME 140 can count the
number of users using location registrations of UEs as substitutes.

[0058]Output section 144 includes the number of users outputted from user
number counting section 143 in an MBMS registration update and sends out
the MBMS registration update to UPE 160.

[0059]FIG. 5 is a block diagram showing a configuration of UPE 160 shown
in FIG. 3. In FIG. 5, input section 161 reports parameter section 162 and
user number counting section 163 of the signals inputted from BM-SC 180,
MME 140 and eNB 120. Especially, input section 161 reports the number of
MBMS users on a per tracking area basis for each service included in the
MBMS registration update to user number counting section 163.

[0060]Parameter section 162 manages various parameters related to data
paths and outputs the service data inputted from BM-SC 180 from output
section 165 according to the parameter setup.

[0061]User number counting section 163 counts the number of joining users,
per service, on a per tracking area basis. Since a plurality of MMEs 140
exist in the MEMS area, the number of users under control of UPE 160 is a
total value of the numbers of users reported from the respective MMES.
Therefore, UPE 160 can know the number of users joining the service that
exist in the MEMS area on a per tracking area basis. User number counting
section 163 having received the MEMS registration update updates the
number of users joining the service and outputs the updated number of
users to user number comparing section 164.

[0062]User number comparing section 164 compares the number of users
outputted from user number counting section 163 with a predetermined
threshold for each tracking area. When the comparison result shows that
the number of users is equal to or greater than the threshold, user
number comparing section 164 selects MCT as a transmission mode in the
tracking area or selects SCT when the number of users is less than the
threshold. An identifier indicating the selected MCT or SCT is outputted
to output section 165.

[0063]Output section 165 as a reporting section outputs the service data
outputted from parameter section 162 and the identifier indicating MCT or
SCT outputted from user number comparing section 164 to eNB 120.

[0064]Next, a procedure for a user to join a multicast subscription group
will be explained. FIG. 6 is a sequence diagram showing a procedure for
joining a multicast subscription group.

[0065]In step (hereinafter abbreviated as "ST") 201, UE 100 which has
received a service announcement sends out a multicast subscription
request to MME 140. This multicast subscription request includes an
identifier indicating a multicast group UE 100 wants to join.

[0066]In ST 202, MME 140 having received the multicast subscription
request performs a procedure for approval of the user jointly with BM-SC
180. This approval procedure is conducted based on the user's subscriber
contract information and judges whether or not the user can receive a
service correctly.

[0067]When the approval procedure is completed successfully, MME 140 sends
out a request for MBMS context activation to UE 100 in ST 203.

[0068]In ST 204, UE 100 having received the MBMS context activation
request sends out an MBMS context activation request to MME 140. The MBMS
context activation request includes performance or the like to receive
MBMS of UE 100 itself.

[0069]When UE 100 is the first to join the multicast group of the service,
MME 140 having received the MBMS context activation request sends out an
MBMS registration request to BM-SC 180 in ST 205. When UE 100 is not the
first to join the multicast group of the service, the processing in ST
205 and ST 206 will not be performed. The MEMS registration request
includes an identifier of UPE 160 to deliver MBMS data.

[0070]In ST 206, BM-SC 180 having received the MEMS registration request
transmits an MBMS registration response including the performance of UE
100 required for the service to MME 140.

[0071]In ST 207, MME 140 counts the number of joining users, per service,
on a per tracking area basis and updates the number of MME users. In ST
208, MME 140 sends out the MBMS registration update to UPE 160. The MBMS
registration update includes the updated number of MBMS users on a per
tracking area basis.

[0072]In ST 209, UPE 160 counts the number of users joining the service
who exist within the MEMS area on a per tracking area basis and updates
the number of UPE users. In ST 210, MME 140 transmits acceptance of MEMS
context activation to the UE.

[0073]The processing described so far completes the procedure for the user
to join the multicast subscription group. The number of MME users is also
updated likewise when the user leaves the multicast group or when the
tracking area of UE 100 is updated and the update result is reported to
UPE 160 and UPE 160 also updates the number of UPE users.

[0074]Next, the session start procedure will be explained using FIG. 7.
Upon detecting the start of a given MEMS service, BM-SC 180 sends out a
session start request to UPE 160 in ST 301.

[0075]In ST 302, user number comparing section 164 of UPE 160 having
received the session start request compares the number of users joining
the service who exist within the MEMS area with a predetermined threshold
for each tracking area. When the number of joining users is equal to or
greater than the threshold, MCT is selected as the transmission mode in
the tracking area and when the number of joining users is less than the
threshold, SCT is selected.

[0076]When MCT is selected, that is, when there are many users in each
tracking area, service notification is sent to eNB 120 and UE 100 via
output section 165 in ST 303 and ST 304, UE 100 is enabled to receive the
service no matter where UE 100 is located in the tracking area and will
not require any subsequent processing.

[0077]On the other hand, when SCT is selected, that is, when there are
only a few users in each tracking area, user number comparing section 164
executes a procedure to check the presence of UEs and counting in the
entire tracking area in ST 303 and ST 304 to deliver MBMS user data only
to eNB 120 in which users exist.

[0078]The session start request in ST 303 includes an identifier
indicating MCT or SCT, and eNB 120 having received the session start
request thereby decides whether to perform service notification or
counting. Furthermore, likewise, the notification/counting report in ST
304 also includes information as to whether or not to perform counting
and UE 100 decides whether or not to respond to the counting.

[0079]Upon receiving information that counting is being performed about
the corresponding service from the service notification on MBMS, UE 100
sets up an RRC connection in eNB 120 in ST 305 to report to eNB 120 that
UE 100 wants to receive the corresponding MBMS. Here, using the RRC
connection request message, UE 100 reports to eNB 120 that UE 100 wants
to receive the corresponding MBMS.

[0080]By recognizing the UE that transferred the RRC connection request
message, eNB 120 recognizes the presence of the user who requests the
specific MBMS within the cell and establishes an MBMS radio bearer in ST
306 when at least one user exists.

[0081]In ST 307, eNB 120 sends out a multicast group joining request to
UPE 160 to construct an IP multicast tree in the IP network between eNB
120 and UPE 160.

[0082]Each IP router and UPE 160, which have received the multicast group
joining request, store output interfaces where users joining the service
exist and thereby transfer the MEMS data only to the necessary output
interfaces.

[0083]The operation described so far completes a series of session start
procedures, and the MEMS data outputted from BM-SC 180 is sent to UPE
160, the MBMS data is sent from UPE 160 only to eNB 120 in which MEMS
users exist and finally sent to UE 100 joining the multicast group.

[0084]Next, the maintenance of the delivery path of the MEMS data set up
by the above described session start will be explained. The RRC
connection between UE 100 and eNB 120 established in ST 305 of the
session start procedure is limited to the control plane that
transmits/receives only control signals.

[0085]Limiting the RRC connection to the control plane refers to a state
in which only the control plane is active, and refers to a state in which
only the entities related to radio link control (RLC) on
transmission/reception of RRC messages and media access control (MAC) are
included and neither reporting (CQI reporting) of channel quality
necessary for transmission/reception of the user plane data of UE 100 nor
monitoring or the like of the downlink common control channel, is
performed.

[0086]Therefore, UE 100 performs no transmission/reception of signals
other than reception of control signals related to MBMS and service data
unless UE 100 moves, and therefore UE 100 can suppress battery
consumption to a low level. Furthermore, the MBMS data is intermittently
received (DRX) at an interval appropriate for the corresponding MBMS and
it is thereby possible to further reduce battery consumption.

[0087]By the way, the state in which only the control plane is active is
limited to between eNB 120 and UE 100 and no information is supplied to
MME 140 which performs position control over UE 100, and therefore MME
140 continues position control over UE 100 on a per tracking area basis.

[0088]eNB 120 can perform position control over UE 100, on a per cell
basis to maintain the RRC connection with UE 100. Therefore, when UE 100
moves to another neighboring eNB, eNB 120 executes a normal handover
procedure and causes the RRC connection with UE 100 to be transferred to
the target eNB. In this way, the target eNB detects that the MBMS user
has moved to come under control of the eNB, outputs, if no such service
has been provided, a multicast group joining request, and provides a new
service. Furthermore, if there is no other UE 100 joining the multicast
group, the source eNB declares withdrawal from the multicast group to UPE
160.

[0089]Normally, UE 100 in the active state measures the received quality
of the neighboring cell and reports the measurement result to eNB 120 on
a regular basis or for each event.

[0090]Here, suppose UE 100 is located in the vicinity of the boundary with
the neighboring cell. eNB 120 having received the neighboring cell
received quality measurement result reported from UE 100 detects that UE
100 is located in the vicinity of the boundary with the neighboring cell.

[0091]Generally, in the case of SCT, received quality of a user located in
cell edges is known to deteriorate. Therefore, when a user is located in
cell edges, the mode is changed from SCT to MCT and inter-cell diversity
combination is performed.

[0092]FIG. 8 is a sequence diagram showing a procedure for mode switching
from SCT to MCT, and FIG. 9 is a block diagram showing the configuration
of eNB 120 according to Embodiment 1 of the present invention. In FIG. 8,
in ST 401, UE 100 measures received quality in nearby cells under
predetermined conditions and reports the measurement result to s-eNB
(i.e. source eNB).

[0093]In ST 402, the s-eNB having received the measurement result detects
that UE 100 is located in the boundary with a given neighboring cell
based on the measurement result, and in ST 403, the s-eNB sends out a
request for joining the multicast group to a t-eNB (i.e. target eNB).

[0094]In ST 404, the t-eNB having received the multicast group joining
request sends out, when there is a resource for the t-eNB to join the
appropriate MBMS, the multicast group joining request to UPE 160 via
output section 125. The multicast group joining request includes an
identifier of the s-eNB and information indicating switching to MCT.

[0095]In ST 405, UPE 160 having received the multicast group joining
request switches the transmission mode from SCT to MCT, performs
scheduling so that the s-eNB and t-eNB can output data in synchronization
with each other in ST 406, and reports the scheduling result to the s-eNB
and t-eNB respectively.

[0096]Parameter sections 122 of the s-eNB and t-eNB which have received
the scheduling result store the reported scheduling information and
reports the scheduling information to output section 125. Output sections
125 of the s-eNB and t-eNB send out MBMS data at timings defined
respectively and UE 100 receives combined signals from a plurality of
cells, and the received quality thereby improves.

[0098]Parameter section 122 manages various parameters set through
signaling with UE 100, MME 140, UPE 160 and eNB 120 and MBMS data is
outputted from output section 125 as a transfer section according to
parameters specified by parameter section 122.

[0099]Cell edge detection section 123 of the s-eNB having received the
measurement result detects that UE 100 is located in the boundary with a
given neighboring cell and outputs an identifier of the neighboring cell
to multicast processing section 124.

[0100]When the own apparatus is the s-eNB, multicast processing section
124 sends out a request for joining the multicast group to the t-eNB that
manages the neighboring cell through output section 125 based on the
identifier of the neighboring cell outputted from cell edge detection
section 123.

[0101]Furthermore, when the own apparatus is the t-eNB, multicast
processing section 124 receives the group joining request and sends out,
when there are resources for joining the MBMS, the multicast group
joining request to UPE 160 through output section 125.

[0102]In this way, Embodiment 1 counts the number of UEs on which tracking
has been conducted for each tracking area including a plurality of cells,
selects MCT when the counted number of UEs is equal to or greater than a
predetermined threshold, or selects SCT when the counted number of UEs is
less than the predetermined threshold, and can thereby appropriately
switch between SCT and MCT according to the number of UEs and can thereby
reduce unnecessary data delivery by MCT, reduce unnecessary counting by
SCT and reduce battery consumption.

[0103]In the present embodiment, UPE 160 compares the number of users
joining the service that exist in the MBMS area with a predetermined
threshold for each tracking area, but the present invention may also be
adapted so that a selected specific MME out of the plurality of existing
MMES compares the number of users likewise.

[0104]The present embodiment detects that UE 100 is located in the
boundary with a given neighboring cell from the received quality
measurement result from UE 100, but the present invention may also be
adapted so that using a NACK prompting retransmission of lost data sent
out to eNB 120 by UE 100 when received quality deteriorates, eNB 120
requests the neighboring cell to join the multicast group upon receiving
the NACK.

[0105]The present embodiment performs processing of comparing the number
of users shown in ST 302 of FIG. 7 using the number of UEs on a per
tracking area basis, but such processing may also be performed per
tracking areas.

Embodiment 2

[0106]Embodiment 2 of the present invention will explain a case where SCT
is selected, counting is performed and then UE 100 transitions to an idle
state again. Since the network cannot specify the movement of UE 100 in
an idle state, recounting (equivalent to counting) is performed on a
regular basis to decide whether to maintain or delete the MBMS radio
bearer, on a per cell basis.

[0107]When counting is performed, since response messages of UEs
requesting MBMS are generally concentrated on an upward channel
simultaneously, interference with and load on the uplink increase, a
probability factor (PF) is provided. Simultaneous responses are avoided
by only UEs that have produced random numbers which are equal to or lower
than the PF value transmitting an RRC response message.

[0108]FIG. 10 is a flowchart showing a recounting procedure by eNB 130
according to Embodiment 2 of the present invention. Furthermore, FIG. 11
is a block diagram showing a configuration of eNB 130 according to
Embodiment 2 of the present invention. Hereinafter, the recounting
procedure will be explained using these figures.

[0110]In ST 501, parameter selection section 132 sets a first PF value
(parameter) upon starting a recounting procedure, and in ST 502,
transmits the first PF value to UE 100 via output section 125 through a
notification/counting report. UE 100 having received the PF value
compares the random number generated by UE 100 itself with the PF value,
transmits a response message when the random number is equal to or below
the PF value or waits until the next PF value is received when the random
number is greater than the PF value.

[0112]In ST 504, cumulative count comparing section 131 as a counting
section counts the cumulative number of received response messages and
compares in ST 505 whether the cumulative count value is equal to or
greater than a predetermined threshold. The process moves to ST 508 when
the cumulative count value is equal to or greater than the threshold
(YES) or moves to ST 506 when the cumulative count value is less than the
threshold (NO).

[0113]In ST 506, cumulative count comparing section 131 decides whether or
not the number of tries of ST 502 to ST 505 has reached a predetermined
number of times (predetermined value). The process moves to ST 509 when
the number of tries has reached the predetermined value (Yes) or moves to
ST 507 when the number of tries has not reached the predetermined value
(No).

[0114]Since the number of tries has not reached the predetermined value in
ST 507, parameter selection section 132 selects a PF value greater than
the PF value used this time. Since a PF value greater than the value this
time is selected on the next try, more UEs 100 are expected to transmit a
response message. After a number of tries, if the decision result in ST
505 shows that the cumulative count value is equal to or greater than the
threshold, cumulative count comparing section 131 commands recounting
period selection section 133 to select a recounting period and commands
parameter selection section 132 to select the first PF value.

[0115]In ST 508, eNB 130 knows that there are relatively many MEMS users
in the cell under control and since the probability that certain users
may continue to stay in the cell is high in the cell where there are many
users, recounting period selection section 133 sets a longer recounting
period. This makes it possible to reduce battery consumption of UE 100.
Furthermore, for the next recounting, parameter selection section 132
sets the first PF value to a small value. This can avoid congestion of
the uplink.

[0116]In ST 506, when the number of tries is decided to have reached the
predetermined value, in ST 509, cumulative count comparing section 131
commands recounting period selection section 133 to select a recounting
period or commands parameter selection section 132 to select the first PF
value next time. eNB 130 knows that there are only a few MBMS users in
the cell under control and since all users may go out of the cell where
there are only a few users, recounting period selection section 133 sets
a shorter recounting period (default value). This makes it possible to
instantaneously detect a case where the number of users in the cell is
reduced to 0 and stop delivery of MBMS data to the cell to thereby
improve the utilization efficiency of radio resources on the entire
network. Furthermore, since the probability that the uplink may be
congested in the next recounting is low, parameter selection section 132
sets the first PF value to a greater value. This makes it possible to
reduce the time required to complete recounting.

[0117]In this way, Embodiment 2 reduces, when the number of users in the
cell is decided to be large according to the recounting conducted in SCT,
the battery consumption of each UE by extending the recounting period and
can reduce interference with and load on the uplink due to simultaneous
responses by reducing the first PF value. On the other hand, when the
number of users in the cell is decided to be small, Embodiment 2 shortens
the recounting period, and can thereby instantaneously detect the case
where the number of users in the cell is reduced to 0 and improve the
utilization efficiency of radio resources on the entire network by
stopping delivery of MBMS data to the corresponding cell and shorten the
time required to complete recounting by increasing the first PF value.

[0118]The present embodiment has explained two cases where the number of
users in the cell is large and small, but the present invention is not
limited to this and it is also possible to control the recounting period
and PF value in two or more cases of the number of users in the cell.

Embodiment 3

[0119]Embodiment 3 of the present invention will explain a case where SCT
is selected, counting is performed and a transmission mode is then
selected again according to the distribution of eNBs 120 where MBMS users
exist.

[0120]FIG. 12 is a block diagram showing the configuration of UPE 170
according to Embodiment 3 of the present invention. However, parts in
FIG. 12 common to those in FIG. 5 will be assigned the same reference
numerals as those in FIG. 5 and detailed explanations thereof will be
omitted.

[0121]In FIG. 12, input section 171 reports signals inputted from BM-SC
180, MME 140 and eNB 120 to parameter section 162, user number counting
section 163 and eNB distribution check section 172. Especially, input
section 171 reports the number of MBMS users on a per tracking area basis
per service included in an MBMS registration update to user number
counting section 163. Furthermore, input section 171 also reports an eNB
identifier included in a multicast group joining request and indicating
eNB 120 in which MEMS users exist to eNB distribution check section 172.

[0122]eNB distribution check section 172 decides a distribution of eNBs
120 where MBMS users exist, that is, a distribution with respect to the
entire tracking area based on eNB identifiers outputted from input
section 171. When the decision result shows that the distribution of eNBs
120 where MBMS users exist satisfies a predetermined condition, eNB
distribution check section 172 selects MCT as the transmission mode in
the tracking area or selects SCT when the condition is not satisfied. An
identifier indicating the selected MCT or SCT is outputted to output
section 173.

[0124]Next, a session start procedure according to Embodiment 3 of the
present invention will be explained using FIG. 13. However, parts in FIG.
13 common to those in FIG. 7 will be assigned the same reference numerals
as those in FIG. 7 and detailed explanations thereof will be omitted.

[0125]In FIG. 13, in ST 601, eNB 120 sends out a multicast group joining
request to UPE 170 in order to construct an IP multicast tree on an IP
network between eNB 120 and UPE 170. In that case, eNB 120 includes the
identifier indicating itself in the multicast group joining request as an
eNB identifier.

[0126]Each IP router having received the multicast group joining request
stores output interfaces where there are users joining the service.

[0127]In ST 602, UPE 170 having received the multicast group joining
request temporarily stores the eNB identifier included in the multicast
group joining request in eNB distribution check section 172 and acquires
multicast group joining request from all eNBs 120 where MBMS users exist
according to the count this time. Here, eNB distribution check section
172 calculates the ratio of the number of eNBs where MBMS users exist to
the total number of eNBs in the entire tracking area. When the ratio is
equal to or greater than a predetermined threshold, eNB distribution
check section 172 selects MCT as the transmission mode in the tracking
area or selects SCT when the ratio is less than the threshold.

[0128]When MCT is selected, the process moves to ST 603 and when SCT is
selected, UPE 170 stores the output interfaces where there are users
joining the service. When SCT is consecutively selected, a series of
session start procedure steps is completed, the MBMS data outputted from
BM-SC 180 is sent to UPE 170, sent from UPE 170 to only eNBs 120 where
MEMS users exist and finally sent to UE 100 joining the multicast group.

[0129]UPE 170 has already reported to eNB 120 in ST 303 that SCT was
selected. Therefore, in ST 603, UPE 170 sends a transmission mode change
report indicating the switching from SCT to MCT to all eNBs 120 in the
tracking area.

[0130]The transmission mode change report in ST 603 includes information
about an identifier indicating MCT or SCT and indicating whether or not
to perform counting and eNB 120 having received the transmission mode
change report thereby decides whether or not to change the transmission
mode and also decides whether or not to on a regular basis perform
counting from this reception onward.

[0131]This completes a series of session start procedure steps and when
there are only a few users per tracking area, yet a few MBMS users are
uniformly distributed with respect to the tracking area, MCT is selected
finally, and therefore UE 100 can receive the service regardless of
locations in the tracking area.

[0132]As explained in Embodiment 1, since the number of users per tracking
area is equal to or greater than a threshold, counting need not be
performed when MCT is selected, but if MCT is selected because the number
of users per tracking area is less than the threshold and a few MBMS
users are distributed uniformly with respect to the tracking area, the
ratio of the number of eNBs where MBMS users exist to the total number of
eNBs in the entire tracking area may also change with the movement of UE
100, and therefore counting is performed on a regular basis. That is, the
processing in ST 304 to ST 601 shown in FIG. 13 is performed on a regular
basis. Thus, UPE 170 performs the eNB distribution decision processing in
ST 608 every time counting is performed and selects the transmission mode
based on the result.

[0133]In this way, according to Embodiment 3, even when the number of
users per tracking area is less than a threshold, if a few MBMS users are
uniformly distributed with respect to the tracking area, switching the
transmission mode from SCT to MCT allows the amount of signaling between
eNBs and between each eNB and the core network apparatus required for
switching the transmission mode from SCT to MCT to be reduced without
reducing the utilization efficiency of radio resources.

[0134]According to the present embodiment, eNB distribution check section
172 switches the transmission mode based on the ratio of the number of
eNBs where MBMS users exist to the total number of eNBs in the entire
tracking area, but it is also possible to set up an eNB identifier and
information about the actual arrangement of eNBs 120 beforehand, decide
the actual distribution situation of eNB 120 where MEMS users exist from
the reported eNB identifier and switch the transmission mode.

[0135]According to the present embodiment, eNB distribution check section
172 switches the transmission mode from the distribution of eNBs 120
where MBMS users exist when counting is performed, but it is also
possible to decide the distribution of eNBs 120 where MBMS users exist
based on the results of several counts and switch the transmission mode.

Embodiment 4

[0136]Embodiment 4 of the present invention will explain the operation of
a cell in cell edges located in the boundary of a tracking area where MCT
is selected.

[0137]In the cell edge of a cell located in the boundary of a tracking
area where MCT is selected, when eNB 120 located in the boundary of the
neighboring tracking area (which corresponds to, for example, eNB 3 and
eNB 5 in FIG. 3) does not provide any service, inter-cell diversity
combination may not be successfully realized and the service received
quality may deteriorate. Therefore, according to the present embodiment,
eNB 120 located in the boundary of a tracking area on a regular basis
inquires of N-eNBs 1 to n located in the boundary of the neighboring
tracking area about the MBMS delivery situation.

[0138]FIG. 14 is a sequence diagram showing inquiries of the MBMS delivery
situation between eNBs 120 located in the boundary between different
tracking areas. Multicast processing section 124 of eNB 120 located in
the boundary of tracking areas is provided beforehand with information
that the own apparatus is located in the boundary of tracking areas.

[0139]In ST 701 in FIG. 14, when providing MBMS in an MCT mode, multicast
processing section 124 of eNB 120 outputs service inquiries to N-eNBs 1
to n located in the boundary between neighboring tracking areas to
inquire about the MBMS delivery situation through output section 125.
Service inquiries include service identifiers indicating the
corresponding MBMS.

[0140]In ST 702, input section 121 of N-eNB 1 to n, having received the
service inquiry, outputs a service identifier to multicast processing
section 124. Multicast processing section 124 decides the delivery
situation of the service specified by the service identifier, includes
the result in a service response and outputs the service response to eNB
120 which sent the service inquiry through output section 125.

[0141]In ST 703, input section 121 of eNB 120, having received the service
responses, outputs the MBMS delivery situations of N-eNBs 1 to n included
in the service responses to multicast processing section 124. Multicast
processing section 124 decides N-eNBs 1 to n that need to join the
corresponding MBMS from the MBMS delivery situations of N-eNBs 1 to n.
Here, "N-eNBs 1 to n that need to join the corresponding MBMS" refer to
N-eNBs 1 to n neighboring a cell which does not provide the corresponding
MBMS and in which there are users requesting MBMS in the neighboring
tracking area.

[0142]N-eNBs 1 to n that need to join the MBMS and eNB 120 which has
specified N-eNBs 1 to n perform the processing in and after ST 403 shown
in FIG. 8 and thereby complete the joining in the MEMS.

[0143]In this way, according to Embodiment 4, eNB 120 located in the
boundary of tracking areas on a regular basis inquiries N-eNBs 1 to n
located in the boundary between neighboring tracking areas about MEMS
delivery situations, causes N-eNBs 1 to n not delivering the MEMS in
question to join the multicast group, and can thereby reduce
deterioration of service received quality of the cell in the cell edge
located in the boundary of tracking areas where MCT is selected.

[0144]The present embodiment on a regular basis inquires of N-eNBs 1 to n
located in the boundary between neighboring tracking areas about the MBMS
delivery situations and thereby decides the necessity for N-eNBs 1 to n
to join the MEMS, but it is also possible to cause all MEMS users
existing in the cell located in the boundary of tracking areas where MCT
is selected to transition to an active state, perform cell edge detection
as in the case of Embodiment 2 and thereby cause N-eNBs 1 to n to join
the MBMS.

Embodiment 5

[0145]Embodiment 5 of the present invention will explain timing UE 100 in
an active state in a cell where SCT is selected sends out a measurement
report.

[0146]UE 100 in an active state in a cell where SCT is selected measures
received quality of a neighboring cell and reports the measurement result
to eNB 200 on a regular basis or event by event. Hereinafter, a report on
a received quality measurement result will be referred to as a
"measurement report." In this way, eNB 200 decides at which edge of the
cell UE 100 is located and requests the corresponding neighboring cell to
join an MCT mode.

[0147]Here, the measurement report is sent on a regular basis or event by
event irrespective of the reception result of MBMS data, that is, whether
or not MBMS data has been received normally. Therefore, UE 100 may send
out unnecessary measurement reports and consume the battery uselessly
despite the fact that MBMS data has been successfully received. On the
contrary, despite the fact that loss of MBMS data has been detected, time
is required until the timing a measurement report is sent out and a state
of poor received quality may continue.

[0148]Therefore, when UE 100 located in cell edges detects data loss of
MBMS, the present embodiment supposes that UE 100 sends out a measurement
report of the neighboring cell to eNB 200 triggered by NACK transmission
for requesting a retransmission of the lost data.

[0149]FIG. 15 is a block diagram showing a configuration of UE 100
according to Embodiment 5 of the pre sent invention. In FIG. 15, input
section 101 outputs an MBMS data packet received from eNB 200 to received
data decision section 102 and a reference signal received from a
neighboring cell to received power measurement section 103 respectively.

[0150]Received data decision section 102 decides whether or not the MBMS
data packet outputted from input section 101 has been correctly received.
When the MEMS data packet has been correctly received, received data
decision section 102 transfers the received packet to a higher layer.
When the MBMS data packet has not been correctly received, that is, loss
of the received data packet is detected, received data decision section
102 creates a NACK message for requesting a retransmission of the lost
data, sends out the created NACK message to eNB 200 through output
section 104 and requests received power measurement section 103 to send
out a measurement report.

[0151]Received power measurement section 103 measures received power for
each neighboring cell using the reference signal outputted from input
section 101, receives the request from received data decision section 102
and sends a measurement report including an identifier of the neighboring
cell and the measurement result of received power to eNB 200 through
output section 104.

[0152]FIG. 16 is a block diagram showing a configuration of eNB 200
according to Embodiment 5 of the present invention. However, parts in
FIG. 16 common to those in FIG. 9 will be assigned the same reference
numerals as those in FIG. 9 and detailed explanations thereof will be
omitted.

[0153]In FIG. 16, input section 201 stores an MBMS data packet received
from UPE 160 in buffer section 202. Furthermore, when a NACK requesting a
retransmission of lost MBMS data and measurement report are received from
UE 100, input section 201 outputs a measurement report to cell edge
detection section 203. When a retransmission of a lost MBMS data packet
is requested from cumulative count comparing section 204, input section
201 transmits the MBMS data packet stored in buffer section 202 to UE 100
again through output section 125.

[0154]Cell edge detection section 203 detects the cell edge bordering on a
neighboring cell at which UE 100 which has sent out the measurement
report is located based on the measurement report inputted from input
section 201 and reports an identifier of the detected neighboring cell to
cumulative count comparing section 204.

[0155]Cumulative count comparing section 204 compares the number of all
users located in the cell edge with a predetermined threshold for each
neighboring cell reported from cell edge detection section 203. When the
comparison result shows that the number of users is equal to or greater
than a threshold, the cumulative count comparing section 204 reports the
identifier of the corresponding neighboring cell to multicast processing
section 124 or requests, when the number of users is less than the
threshold, input section 201 to retransmit an MBMS data packet
corresponding to the NACK out of the MBMS data packets stored in buffer
section 202.

[0156]The operations of cumulative count comparing section 204 after
reporting the identifier of the neighboring cell to multicast processing
section 124 are the same as the operations in and after ST 403 in FIG. 8
and therefore explanations thereof will be omitted.

[0157]In this way, according to Embodiment 5, when UE 100 located in cell
edges detects loss of an MEMS data packet, UE 100 sends a measurement
report of the neighboring cell triggered by NACK transmission requesting
a retransmission of the lost data, thereby sends out the measurement
report to eNB 200 only in case of necessity, and can thereby suppress the
amount of battery consumption of UE 100 to a low level. Furthermore, when
there are many users in the vicinity of the cell edge, it is possible to
efficiently improve the user's received service quality by switching from
SCT to MCT.

[0158]The present embodiment has explained on the assumption that a NACK
for requesting a retransmission of a lost MBMS data packet and
measurement report are transmitted separately, but a NACK and measurement
report may also be transmitted as one message.

Embodiment 6

[0159]Embodiment 6 of the present invention will explain a method of
efficiently counting the number of users existing in the vicinity of cell
edges bordering on a specific neighboring cell.

[0160]Embodiment 5 compares the number of all users existing in the
vicinity of cell edges with a predetermined threshold for each
neighboring cell and requests the corresponding neighboring cell to
perform switching to MCT when the number of users is equal to or greater
than the threshold. However, there exist cell edges corresponding in
number to neighboring cells and since it takes time for all users located
in the vicinity of the cell edge to uniformly send measurement reports
and for the number of users located in the vicinity of the cell edge
bordering on a specific neighboring cell to reach the threshold,
inefficient retransmissions may be repeated. Therefore, the present
embodiment limits transmissions of measurement reports to users located
in the vicinity of an edge with a specific neighboring cell.

[0161]Hereinafter, a method of sending a measurement report according to
the present embodiment will be explained using FIG. 15 and FIG. 16.

[0162]In eNB 200 shown in FIG. 16, parameter selection section 132 selects
a cell identifier of a neighboring cell at predetermined intervals and
transmits the selected cell identifier to UE 100 through output section
125. The cell identifier is used to specify a UE that sends out a
measurement report amongst the UEs located in the vicinity of cell edges
and have detected loss of MBMS data packets.

[0163]In UE 100 shown in FIG. 15, input section 101 reports the cell
identifier received from eNB 200 to received power measurement section
103. Received data decision section 102 which has detected the loss of
the MBMS data packet requests received power measurement section 103 to
send out a measurement report.

[0164]Received power measurement section 103 decides whether or not
information about the neighboring cell corresponding to the cell
identifier reported from input section 101 is included in the measurement
report to be sent out. When information about the neighboring cells is
included, received power measurement section 103 sends out the
measurement report to eNB 200 or stops, when information about the
neighboring cells is not included, transmission of the measurement
report. The subsequent operations of eNB 200 of threshold decision and
switching to MCT are the same as those in Embodiment 5, and therefore
detailed explanations thereof will be omitted.

[0165]In this way, Embodiment 6 authorizes only UEs located in the
vicinity of cell edges bordering on a specific neighboring cell out of
UEs, which are located in the vicinity of the cell edge and have detected
loss of an MBMS data packet, to send a measurement report, and can
thereby efficiently count the number of users present in cell edges
bordering on the specific neighboring cell and promptly perform switching
from SCT to MCT for the corresponding neighboring cell.

[0166]According to the present embodiment, parameter selection section 132
selects a cell identifier of a neighboring cell at predetermined
intervals, but it is also possible to consecutively select only an
identifier of a cell neighboring a cell edge which is predicted to have
poor received quality.

[0167]The present embodiment authorizes only users located in the vicinity
of cell edges bordering on a specific neighboring cell out of the users
having detected loss of an MEMS data packet to send a measurement report,
but it is also possible to further combine the PFs explained in
Embodiment 2 and perform control so as to prevent many measurement
reports from being sent out simultaneously.

[0168]Also, although cases have been described with the above embodiment
as examples where the present invention is configured by hardware, the
present invention can also be realized by software.

[0169]Each function block employed in the description of each of the
aforementioned embodiments may typically be implemented as an LSI
constituted by an integrated circuit. These may be individual chips or
partially or totally contained on a single chip. "LSI" is adopted here
but this may also be referred to as "IC," "system LSI," "super LSI," or
"ultra LSI" depending on differing extents of integration.

[0170]Further, the method of circuit integration is not limited to LSI's,
and implementation using dedicated circuitry or general purpose
processors is also possible. After LSI manufacture, utilization of a
programmable FPGA (Field Programmable Gate Array) or a reconfigurable
processor where connections and settings of circuit cells within an LSI
can be reconfigured is also possible.

[0171]Further, if integrated circuit technology comes out to replace LSI's
as a result of the advancement of semiconductor technology or a
derivative other technology, it is naturally also possible to carry out
function block integration using this technology. Application of
biotechnology is also possible.

[0172]The disclosures of Japanese Patent Application No. 2006-229811,
filed on Aug. 25, 2006, Japanese Patent Application No. 2006-274080,
filed on Oct. 5, 2006 and Japanese Patent Application No. 2006-310271,
filed on Nov. 16, 2006, including the specifications, drawings and
abstracts, are incorporated herein by reference in their entirety.

INDUSTRY APPLICABILITY

[0173]The core network apparatus, radio communication base station
apparatus and radio communication method according to the present
invention can improve the utilization efficiency of radio resources of an
entire network without increasing battery consumption of UEs and are
applicable to a transmission control system that delivers MBMS.